Exam 2 Slideshow 6 Flashcards
Inertia =
Mass =
Inertia = Resistance to motion
Mass = Measure of body’s linear intertia
Kinetics =
cause of motion
Centric forces cause =
linear (translational) motion only (Float Serve)
Eccentric (off-center) forces =
always cause rotational motion
(sometimes linear motion, too) (Jump topspin serve)
Eccentric Forces: Torque
(a.k.a. moment of force)
Torque is the turning or rotational
effect of an eccentric force
Units: Nm
Torque at a given joint
is a measure of =
strength
Net Torque
Torques acting around the same
axis may be summed
Momentum Arm
The moment arm can change
based on the position of the
segment/object
Center of Gravity
COG is location of axis of
rotation when airborne
Can move outside of body
Four Properties of a Fluid
Pressure
Density
Specific Weight
Viscosity
Types of Flow
Laminar
Turbulent
Laminar
FLUID MOLECULES FLOWING
PARALLEL TO ONE ANOTHER
- “SMOOTH”
- “ORDERED”
Turbulent
- FLUID MOLECULES MIX IN A
RANDOM MANNER - “CHAOTIC”
- “UNORDERED”
BUOYANCY
- AN UPWARD FORCE
- A “FLUID REACTION FORCE”
ARCHIMEDES PRINCIPLE
How does the free body diagram look?
THE BUOYANT FORCE IS EQUAL TO THE
WEIGHT OF THE FLUID DISPLACED BY THE BODY
*F B = V D y
* y = SPECIFIC WEIGHT OF FLUID
Buoyancy and weight arrows go in opposite directions
BUOYANT FORCE in Fluid
- IF A BODY IS IMMERSED IN A FLUID IT WILL ALWAYS
EXPERIENCE A BUOYANT FORCE EVEN IF IT IS NOT MOVING
DYNAMIC FLUID FORCES
MOTION BETWEEN THE FLUID AND THE BODY OCCURS
LIFT FORCE
- FORCE ACTING PERPENDICULAR TO FLUID FLOW (RELATIVE FLOW)
- 90 degrees TO MOTION
- “LIFTS” BODY
DRAG FORCE
- FORCE ACTING IN DIRECTION OF FLUID FLOW (RELATIVE FLOW)
- OPPOSES MOTION
- SLOWS BODY
RELATIVE VELOCITY =
VELOCITY OF BODY RELATIVE TO THE FLUID
VFLUID – VBODY
Drag
- FORCE ACTING IN DIRECTION OF
FLUID FLOW (RELATIVE FLOW) - OPPOSES MOTION
- SLOWS BODY
Types of Drag Forces
Surface
Form
Types of Drag Forces
Surface
FORCE ACTING ON SURFACE OF BODY OR OBJECT (“SKIN FRICTION”)
Types of Drag Forces
Form
FORCE CREATED BY PRESSURE DIFFERENCE BETWEEN FRONT AND BACK
SIDES OF A BODY IN RELATIVE MOTION
Lift
- FORCE ACTING
PERPENDICULAR(90O ) TO FLUID
FLOW (RELATIVE FLOW) - “LIFTS” BODY
Bernoulli’s Principle
High velocity
corresponds with
Low velocity
corresponds to
High velocity
corresponds with
decreased pressure
Low velocity
corresponds to high
pressure
MAGNUS EFFECT
- DEVIATION IN TRAJECTORY OF A SPINNING OBJECT TOWARD THE DIRECTION OF SPIN
